Apparatus for actuating a work gripping device

ABSTRACT

An apparatus for actuating a collet or other chucking devices which includes a rotatable cylinder and double acting piston assembly positioned around a tubular draw member for causing a collet or the like to reciprocate in a lathe spindle. The piston, which is rigidly secured to the drawing member, is provided with a pair of spring-biased, piston operated valves for admitting fluid under pressure to the expansible chambers defined by the piston and the cylinder walls as well as venting the same for the purpose of causing the piston to reciprocate in the cylinder. The valves also include check means for trapping fluid under pressure in either of the chambers should the pressure of the fluid source be reduced. The drawing member generally comprises two concentric tubes, the inner one having a pair of slots in its external surface which cooperate with the internal surface of the outer tube to form a pair of passageways for providing fluid under pressure to the aforementioned expansible chambers.

United States Patent [191 Parsons et al.

[ Dec. 9, 1975 APPARATUS FOR ACTUATING A WORK GRIPPING DEVICE [73] Assignee: Hardinge Brothers, Inc., Elmira,

[22] Filed: Aug. 3, 1973 [21] Appl. No.: 385,549

[52] US. Cl. 91/420; 91/422; 92/106; 279/4 [51] Int. Cl. F15B 11/08; F15B 13/042 [58] Field of Search 91/420, 422, 222; 92/106, 92/111; 279/4 Primary Examiner-lrwin C. Cohen Attorney, Agent, or FirmSh1esinger, Arkwright, Garvey & Dinsmore [57] ABSTRACT An apparatus for actuating a collet or other chucking devices which includes a rotatable cylinder and double acting piston assembly positioned around a tubular draw member for causing a collet or the like to reciprocate in a lathe spindle. The piston, which is rigidly secured to the drawing member, is provided with a pair of spring-biased, piston operated valves for admitting fluid under pressure to the expansible chambers defined by the piston and the cylinder walls as well as venting the same for the purpose of causing the piston to reciprocate in the cylinder. The valves also include check means for trapping fluid under pressure in either of the chambers should the pressure of the fluid source be reduced. The drawing member generally comprises two concentric tubes, the inner one having a pair of slots in its external surface which cooperate with the internal surface of the outer tube to form a pair of passageways for providing fluid under pressure to the aforementioned expansible chambers.

9 Claims, 7 Drawing Figures US. Patent Dec. 9 1975 Sheet 1 of2 3,924,514

APPARATUS FOR ACTUATING A WORK GRIPPING DEVICE BACKGROUND OF THE INVENTION This invention relates generally to apparatus for opening and closing collets or other chucking devices.

A serious problem with rotating machinery such as lathes having a collet or chuck closed by fluid pressure means occurs when there is an inadvertent drop in the pressure of the working fluid. If there is a reduction in the force which holds the jaws closed, the tool or workpiece may fly off the rotating spindle thereby causing serious injury to the operator.

Benjamin et a1, U.S. Pat. No. 3,364,823, Jan. 23, 1968, discloses one solution for the problem by means of an arrangement wherein fluid is trapped in one of the expansible chambers formed by the piston and cylinder walls through the action of a check valve and spool valve combination mounted in the cylinder housing. One drawback to this arrangement is that the placement of the valve means in the cylinder substantially increases the radial dimension and, thus, the rotational inertia of the unit for a piston of given size.

Often in fluid operated work gripping devices of this type, common means for conveying the fluid from the bearing to the expansible chambers are passageways bored in the wall of the draw tube as disclosed in Blattry U.S. Pat. No. 3,369,464. One disadvantage to this design, however, is that the wall thickness of the drawing member must be sufficiently thick to accommodate the passageways. Any increase in the wall thickness and diameter of the drawing tube, necessitates either the use of larger mechanical bearings, or a reduction in the inner diameter of the tube with a resulting limitation on the size of workpiece which can be accommodated thereby.

OBJECTS OF THE INVENTION It is, therefore, an object of this invention to provide an apparatus for acutatin g a work gripping device which is capable of maintaining a collet or the like in work gripping position even though the pressure of the working fluid should be reduced.

Another object of this invention is to provide an apparatus for actuating a work gripping device including a fluid operated drawing member having an operating piston with maximum pressure surface area received in a cylinder having minimum radial dimensions.

A further object of this invention is to provide an apparatus for actuating a work gripping device having relatively small rotational inertia.

A further object of this invention is to provide an apparatus for actuating a work gripping device wherein rotational imbalance is minimized.

A still further object of this invention is to provide an apparatus for actuating a work gripping device including a tubular drawing member having a relatively small outer diameter for a given inner diameter.

Still another object of this invention is to provide an apparatus for actuating a work gripping device including a drawing member which may be readily and efficiently manufactured.

SUMMARY OF THE INVENTION The invention relates to a device for actuating a work gripping collet including a housing adapted to be mounted on a machine tool spindle, a cylinder within the housing, a collet drawing member mounted in the housing for axial movement relative thereto, and a double acting piston slidably received in the cylinder. The piston includes first and second valve assemblies for admitting pressurized fluid to the expansible chambers formed by the piston faces and the inner walls of the cylinder. The valve assemblies also include means for venting one of the chambers when pressurized fluid is introduced into the other as well as check means for trapping fluid in the pressurized chamber should the pressure of the fluid source be reduced. The device further includes a ball bearing joint as well as passageways in the drawing member to convey the pressurized fluid from the bearing joint to the expansible chambers. The drawing member comprises two concentric tubes, the aforementioned passageways being formed by a pair of slots milled in the external surface of the inner tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a collet actuating device embodying the present invention with a portion thereof shown in elevation;

FIG. 2 is a fragmentary enlarged sectional view of the collet actuating device illustrated in FIG. 1;

FIG. 3 is a longitudinal sectional view of the drawing member forming a part of the present invention;

FIG. 4 is a fragmentary top plan view of the drawing member illustrated in FIG. 3;

FIG. 5 is a fragmentary bottom plan view of the drawing member illustrated in FIG. 3;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 4, and viewed in the direction of the arrows;

FIG. 7 is a sectional view similar to the view of FIG. 1 illustrating the present invention in relation to a lathe spindle and work gripping collet, the latter being in its closed position.

DETAILED DESCRIPTION OF THE INVENTION SHOWN IN FIGS. 1 THROUGH 7 The device for opening and closing the through hole collet 10 comprises generally a tubular drawing member 12, a rotatable cylinder 18 positioned around drawing member 12, a double acting annular piston 16 slidably received in the cylinder 18, and a ball bearing joint 20.

The drawing member 12 is mounted in cylinder 18 for axial movement relative thereto with seals or gaskets 22 and 24 sealing the interior of cylinder 18 as the external surfaces 26 and 28 of concentric tubular members 30 and 32, respectively, slide relative to the annular surfaces 34 and 36 of cylinder 18. The double acting piston 16 is frictionally secured to the drawing member 12 by means of a spanner nut 38 which is threaded on tubular member 30. Head 40 is secured to cylinder 18 by means of bolts such as 42 while the cylinder 18 is mounted on the lathe spindle sleeve 44 by means of adjusting ring 46 and bolts such as 48. By these means, the spindle 50, sleeve 44, cylinder 18, piston 16 and drawing member 12 may rotate as a unit about the longitudinal axis of drawing member 12.

Referring particularly to FIGS. 3 through 6, the drawing member 12 comprises an inner tubular member 32 threadedly secured to draw tube 52, and an outer tubular member 30 which is frictionally or otherwise secured to member 32. The preferred method of accomplishing this is to shrink member 30 over member 32. A pair of grooves or slots 54 and 56 are milled 3 in the external surface of inner tubular member 32 and are preferably circumferentially displaced by 180. Apertures 58 and 60 in member 30 are positioned above slot 54 and apertures 62 and 64 are positioned above slot 56. Since the internal surface 66 of member 30 tightly engages the external surface 28 of member 32 and is flush therewith, a pair of fluid-tight passageways or conduits 68 and 70 are formed in drawing member 12 and are in open communication with the ports formed by apertures 58, 60, 62, and 64, respectively. Because the passageways 68 and 70 are formed by milling the external surface of an inner tube 32 rather than by drilling a longitudinal passage in the wall of the drawing member 12, the fluid conduits 68 and 70 so formed may have a relatively large cross-sectional area without requiring an increase in the overall wall thickness of the drawing member 12.

The rear portion 72 of drawing member 12 supports ball bearing joint containing bearings 74 and 76. A fluid, such as air, is introduced under pressure through stationary hoses at inlets 80 or 82 to the longitudinally displaced annular passageways 84 or 86 formed in the internal surface 88 of member 20. A portion of external surface 26 of member 30 conforms generally to the internal surface 88 of member 20 but the outer diameter of the former is slightly less than the inner diameter of the latter thereby forming a small annular gap 90 which may be of the order of 0.0005 inches wide. When a fluid under pressure is introduced into gap 90 through inlets 80 or 82 and their respective passageways 84 or 86, a very small and harmless leakage can take place through it.

Piston 16 is provided with opposite faces 92 and 94 which cooperate with the internal walls 96 of cylinder 18 to form two expansible chambers 98 (FIG. 1) and 100 (FIG. 7). Valve assemblies 102 and 104 are mounted in piston 16 for reciprocating movement in a direction parallel to the axis of rotation of the cylinder, piston and drawing member assembly. Valves 102 and 104 include check valves 106 and 108 positioned in chambers 110 and 112. The check valves 106, 108 are biased to their closed position by springs 114 and 115 supported by annular retainers 116 and 117 positioned by lock rings 118 and 119. O-rings 129 provide a seal when the valves 106 and 108 are seated. The check valves 106 and 108 are each provided with radial ribs 122 and 124, respectively, and connecting slots 125 in the faces between which fluid may flow when the valves are unseated. The ribs 122, 124 also serve to support the check valves 106, 108. Fluid may be introduced into chamber 98 from passageway 70 through aperture 64 into the passageway 131 formed in piston 16, through the annular passageway 128 and then around check valve 108 in the channels or openings formed between the radially extending ribs 124 and slots 125 in the faces. Fluid under pressure may be introduced to expansible chamber 100 from passageway 68 through aperture 60 into piston passageway 130, through annular passageway 126 and then around check valve 106 through the channels or spaces formed by ribs 122 and slots 125 in the faces.

Valve actuating pistons 134, 135 having stems 136 and 137 are received in annular cylinders 138 and 139 respectively and retained by lock rings 140, and 141. O-rings 148 provide a seal when pistons 134 and 135 are seated. The expansible chambers 98 and 100 are sealed from each other by means of compression seals 142 and 144 as well as pistons 134 and 135, the latter being snugly received in cylinders 138 and 139. The piston 16 is held against rotation relative to cylinder 18 by means of a pin 146 (see FIG. 2).

OPERATION To close collet 10 by drawing it rearwardly in spindle 50 thereby closing its work gripping jaws 148, a fluid under pressure is introduced at inlet 82, through passageways 86, 58, 68, 60, 130 and 126, and around check valve 106 to expansible chamber 100. The increased pressure in chamber 100 will force piston 135 to the left thereby unseating check valve 108 and venting chamber 98 through passageways 128, 131, 64, 70, 62, 84, and 80. At the same time, piston 16 will be forced to the left carrying drawing member 12 with it thereby drawing collet 10 within spindle 50. This action will cause the work gripping jaws 148 to close. Since valve 106 is a check valve, should there be an inadvertent loss in fluid pressure at passageway 126, no fluid can escape from chamber 100 due to the fact that spring 114 will have caused check valve 106 to seat when pressure equilibrium was established. When piston 16 has been moved to its leftmost position, it cannot return unless fluid under pressure is introduced into chamber 98 in a manner which will now be described.

Should it be desired to open collet 10 by moving the drawing member 12 to the right, fluid under pressure is introduced at inlet and inlet 82 is vented. The fluid under pressure flows through passageways 84, 62, 70, 64, 131, and 128, around check valve 108 and into expansible chamber 98. The increased pressure in chamber 98 forces piston 134 to the right causing stem 136 to unseat valve 106 thereby venting chamber 100 through passageways 126, 130, 60, 68, 58, and 86. At the same time, piston 16 is forced to the right and check valve 108 will close when pressure equilibrium has been reached, thereby trapping the pressurized fluid in chamber 98 until such time as fluid under pressure is introduced to inlet 82.

The same fluid which operates the collet closing mechanism just described is admitted to the annular gap between the non-rotating support member 20 and the rotating drawing member 12 through which a very small and harmless leakage takes place. Under conditions where collet 10 is closed, the fluid under pressure is admitted through inlet 82 and vented through inlet 80 by any appropriate means such as a four-way valve.

The unitary assembly of spindle 50, collet 10, drawing member 12, piston 16 and cylinder 18 may be rotated by any appropriate means well known in the art.

While this invention has been described as having a preferred design, it will be understood that it is capable of further modification. This application is, therefore, intended to cover any variations, uses and/or adaptations of the invention following the general principles of this invention and including such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and as may be applied to the essential features hereinbefore set forth and fall within the scope of this invention or the limits of the appended claims.

What is claimed is:

1. A device for actuating a work gripping collet comprising:

a. a cylinder adapted to be mounted to a machine tool spindle,

5. b. a tubular through hole collet drawing member being mounted within said cylinder for axial movement relative thereto, a c. annular piston means slideably received in 'said cylinder and including means for axially moving said member relative to said cylinder,

d. said drawing'member passing through said piston means, I v

e. said piston means having a firstpressure face cooperating with one end of said cylinder to form a first expansible chamber and having "a second pressure face cooperating with the other end of said cylinder to form a second expansible chamben-rf. said piston means including first valve means for admitting fluid under pressure to said first.cha'mber, said first valve means being entirely supported by said piston means and movable therewith,

g. said first valve means extending through said piston and forming a portion of said first and second pressure faces,

h. said piston means including second valve means for admitting fluid under pressure to said second chamber, said second valve means being entirely supported by said piston means and movable therewith,

i. said second valve means extending through said piston and forming a portion of said first and second pressure faces,

j. said first valve means including means for venting said first chamber when fluid under pressure is admitted to said second chamber and said second valve means including means for venting said second chamber when fluid under pressure is admitted to said first chamber,

k. means for alternatively connecting a source of fluid under pressure to said first and second chambers through said first and second valve means, respectively,

I. said first valve means including means for trapping fluid in said first chamber when the pressure of the source of fluid under pressure is reduced while said first chamber is connected to the source of fluid under pressure,

m. said piston means, cylinder and drawing member being mounted for unitary rotation,

n. said first and second valve means being mounted in said piston means radially outward of the axis of rotation of said piston means, cylinder and drawing member for movement relative thereto in a direc tion parallel to said axis of rotation, and

0. each of said first and second valve means including a pressure responsive valve piston having a face thereof forming said pressure face portion.

2. A device for actuating a work gripping collet as in claim 1 and wherein said means for connecting a source of fluid under pressure to said first and second chambers includes first and second longitudinal passageways in said drawing member.

3. a device for actuating a work gripping collet as in claim 1 and wherein:

a. each said valve means includes a first and springbiased, valve piston operated valve.

4. A device for actuating a work gripping collet as in claim 1 and wherein:

a. said means for trapping fluid includes a check valve.

5. A device for actuating a work gripping collet comprising:

s.--a' cylinderadapted to be mounted to a machine tool spindle; b. a tubular through hole collet drawing member beingi'mou'nted within said cylinder for axial movement relative thereto, 1 c. said drawing member comprising: i 1

a first tubular member having an external surface and including means at one end for securing a work gripping collet thereto,

first and second slots inthe external surface of said first tubular member, i

a second tubular member having internal and ex- -temal surfaces and being concentrically positioned around and-rigidly secured to said first member,

thejinternal surface of said second member being flush with the external surface, of said first member thereby forming a pair of fluid-tight passageways,

first and second longitudinally displaced apertures in said second member positioned above one of said slots,

third and fourth longitudinally displaced apertures in said second member positioned above the other said slots,

d. annular piston means slideably received in said cylinder and including means for axially moving said member relative to said cylinder.

e. said drawing member passing through said piston means,

f. said piston means having a first pressure face cooperating with one end of said cylinder to form a first expansible chamber and having a second pressure face cooperating with the other end of said cylinder to form a second expansible chamber,

g. said piston means including first valve means for admitting fluid under pressure to said first chamber and second valve means for admitting fluid under pressure to said second chamber,

h. said first and second valve means being entirely supported by said piston means and movable therewith to form a portion of said first and second pressure faces,

i. said first valve means including means for venting saidfirst chamber when fluid under pressure is admitted to said second chamber and said second valve means including means for venting said second chamber when fluid under pressure is admitted to said first chamber, and

j. means for alternatively connecting a source of fluid under pressure to said first and second chambers through said first and second valve means, respectively,

k. said first valve means including means for trapping fluid in said first chamber when the pressure of the source of fluid under pressure is reduced while said first chamber is connected to the source of fluid under pressure,

1. said piston means, cylinder and drawing member being mounted for unitary rotation,

m. said first and second valve means being mounted in said piston means radially outward of the axis of rotation of said piston means, cylinder and drawing member for movement relative thereto in a direction parallel to said axis of rotation.

6. A device for actuating a work gripping collet as in claim 5 and wherein:

a. said piston is provided with first passageway means for connecting one of said fluid-tightpassageways to one of said chambers, and

b. said piston is provided with second passageway means for connecting the other of said fluid-tight passageways to the other of said chambers.

7. A device for actuating a work gripping collet as in claim 6 and wherein:

a. said second and fourth apertures are in communication with said passageway means.

8. A device for actuating a work gripping collet as in claim 7 and wherein:

a. said first and third apertures are longitudinally displaced from each other along said second tubular members.

9. A device for actuating a work gripping collet as in claim and including:

8 a. a sleeve being positioned around said second tubular member and having an internal surface conforming generally to the external surface of said second tubular member but being slightly radially spaced therefrom thereby forming an annular source of fluid under pressure. r i i I 

1. A device for actuating a work gripping collet comprising: a. a cylinder adapted to be mounted to a machine tool spindle, b. a tubular through hole collet drawing member being mounted within said cylinder for axial movement relative thereto, c. annular piston means slideably received in said cylinder and including means for axially moving said member relative to said cylinder, d. said drawing member passing through said piston means, e. said piston means having a first pressure face cooperating with one end of said cylinder to form a first expansible chamber and having a second pressure face cooperating with the other end of said cylinder to form a second expansible chamber, f. said piston means including first valve means for admitting fluid under pressure to said first chamber, said first valve means being entirely supported by said piston means and movable therewith, g. said first valve means extending through said piston and forming a portion of said first and second pressure faces, h. said piston means including second valve means for admitting fluid under pressure to said secoNd chamber, said second valve means being entirely supported by said piston means and movable therewith, i. said second valve means extending through said piston and forming a portion of said first and second pressure faces, j. said first valve means including means for venting said first chamber when fluid under pressure is admitted to said second chamber and said second valve means including means for venting said second chamber when fluid under pressure is admitted to said first chamber, k. means for alternatively connecting a source of fluid under pressure to said first and second chambers through said first and second valve means, respectively, l. said first valve means including means for trapping fluid in said first chamber when the pressure of the source of fluid under pressure is reduced while said first chamber is connected to the source of fluid under pressure, m. said piston means, cylinder and drawing member being mounted for unitary rotation, n. said first and second valve means being mounted in said piston means radially outward of the axis of rotation of said piston means, cylinder and drawing member for movement relative thereto in a direction parallel to said axis of rotation, and o. each of said first and second valve means including a pressure responsive valve piston having a face thereof forming said pressure face portion.
 2. A device for actuating a work gripping collet as in claim 1 and wherein said means for connecting a source of fluid under pressure to said first and second chambers includes first and second longitudinal passageways in said drawing member.
 3. a device for actuating a work gripping collet as in claim 1 and wherein: a. each said valve means includes a first and springbiased, valve piston operated valve.
 4. A device for actuating a work gripping collet as in claim 1 and wherein: a. said means for trapping fluid includes a check valve.
 5. A device for actuating a work gripping collet comprising: a. a cylinder adapted to be mounted to a machine tool spindle, b. a tubular through hole collet drawing member being mounted within said cylinder for axial movement relative thereto, c. said drawing member comprising: a first tubular member having an external surface and including means at one end for securing a work gripping collet thereto, first and second slots in the external surface of said first tubular member, a second tubular member having internal and external surfaces and being concentrically positioned around and rigidly secured to said first member, the internal surface of said second member being flush with the external surface of said first member thereby forming a pair of fluid-tight passageways, first and second longitudinally displaced apertures in said second member positioned above one of said slots, third and fourth longitudinally displaced apertures in said second member positioned above the other said slots, d. annular piston means slideably received in said cylinder and including means for axially moving said member relative to said cylinder. e. said drawing member passing through said piston means, f. said piston means having a first pressure face cooperating with one end of said cylinder to form a first expansible chamber and having a second pressure face cooperating with the other end of said cylinder to form a second expansible chamber, g. said piston means including first valve means for admitting fluid under pressure to said first chamber and second valve means for admitting fluid under pressure to said second chamber, h. said first and second valve means being entirely supported by said piston means and movable therewith to form a portion of said first and second pressure faces, i. said first valve means including means for venting said first chamber when fluid under pressure is admitted to said second chamber and said second valve means including means for venting said second chamBer when fluid under pressure is admitted to said first chamber, and j. means for alternatively connecting a source of fluid under pressure to said first and second chambers through said first and second valve means, respectively, k. said first valve means including means for trapping fluid in said first chamber when the pressure of the source of fluid under pressure is reduced while said first chamber is connected to the source of fluid under pressure, l. said piston means, cylinder and drawing member being mounted for unitary rotation, m. said first and second valve means being mounted in said piston means radially outward of the axis of rotation of said piston means, cylinder and drawing member for movement relative thereto in a direction parallel to said axis of rotation.
 6. A device for actuating a work gripping collet as in claim 5 and wherein: a. said piston is provided with first passageway means for connecting one of said fluid-tight passageways to one of said chambers, and b. said piston is provided with second passageway means for connecting the other of said fluid-tight passageways to the other of said chambers.
 7. A device for actuating a work gripping collet as in claim 6 and wherein: a. said second and fourth apertures are in communication with said passageway means.
 8. A device for actuating a work gripping collet as in claim 7 and wherein: a. said first and third apertures are longitudinally displaced from each other along said second tubular members.
 9. A device for actuating a work gripping collet as in claim 5 and including: a. a sleeve being positioned around said second tubular member and having an internal surface conforming generally to the external surface of said second tubular member but being slightly radially spaced therefrom thereby forming an annular space between the external surface of said second tubular member and the internal surface of said sleeve, b. means for permitting said tubular members to rotate within said sleeve, c. said first and second longitudinally displaced grooves in the internal surface of said sleeve being positioned above said first and third apertures at all positions of rotation of said tubular members, and d. means for connecting each of said grooves to a source of fluid under pressure. 